This "Cold Blooded" Killer Stabbed a Florida Grandmother to Death in Her Garage

Seventy-eight year old Ina Gross was like a ray of sunshine.

The devoted grandmother and community volunteer lit up every room she walked into.

“My mother was my best friend,” her daughter Ellen Gerth told Oxygen’s Killer Relationship with Faith Jenkins. “She was my soul mate. She was funny, she was compassionate, she was loving, she was kind.”

But on January 9, 2012, Ina was found murdered in the garage of her Florida home with her throat slit.

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“I kept hoping that this was just a bad dream, this hadn’t really happened,” Gerth said of receiving devastating news.

Tom had been visiting his mom for a few days from his home in Israel to attend a dedication ceremony in honor of his father, Samuel Gross, an accomplished pediatric hematologist and oncologist who died a year before.

“My parents were really like the dynamic duo because they were both really interesting people, very bright people, educated, compassionate,” Gerth told the show. “My father was world-renowned in the field of pediatric hematology and oncology. He was one of the earliest to launch bone marrow transplants.”

The couple was married for 58 years before Sam got a devastating cancer diagnosis. Although Ina was “absolutely heartbroken,” Gerth said she was determined to continue to try to enjoy life, and was active in the Lakewood Ranch community where she lived when she was brutally killed.

Tom told detectives the night before, he and his mother had gone to the movies, then came home and had some left-over chili.

“My mother likes to drink wine. She had a, I don’t know, a glass or two of white wine. I had a little white wine,” he told detectives, according to a recording of his interview with detectives.

According to Tom, he went to bed around 10:45 p.m. and woke up early the next morning to catch his flight back home. He saw Ina’s dog Nicky in the garage and went to investigate, only to discover his mom’s bloody body.

“I saw her. I wanted to puke,” Tom said.

Tom told detectives he didn’t vomit, but strangely authorities did find vomit inside the front seat of Ina’s car inside the garage, although it wasn’t clear who it had come from.

According to Detective John Kenney, now retired, Ina was found lying on the ground in “a large pool of blood” with multiple stab wounds.

Detectives investigate potential suspects

“It only takes one knife wound in the jugular to kill somebody, well Ina’s case it was multiple stab wounds,” he said. “Usually overkill is something of passion, someone’s vindictive, someone’s angry.”

Tom told authorities he awoke to find the front door of the home ajar and theorized that his mom must have been killed by an intruder.

At the scene, Detective Stephen Ives noted that it appeared the murder weapon was a kitchen knife that came from inside the house.

“As I walk through the kitchen, I can see that there is a glass of wine sitting on the countertop and there’s a large knife array,” Ives recalled. “The murder weapon appeared to be consistent with the knives that are in this set, sitting on the counter.”

Gerth believed the killer may have been a homeless man who had done some computer work at her mother’s house shortly before her death.

“Apparently she had hired this gentleman on several occasions to do some computer work and he and Ina had a bit of a falling out, had some friction regarding the payment for his services which irritated him,” Ives said.

Although it took a while for authorities to find the man, they eventually tracked him to Venice, where he admitted to knowing Ina and doing work for her, but insisted there wasn’t any long-standing friction between them.

Ina Gross, featured on Killer Relationship With Faith Jenkins 209 Photo: Oxygen

Detectives also learned that at the time of the murder he had been staying in Sarasota with a woman who confirmed his alibi.

Investigators also considered whether Ina’s death was linked to the Sarasota death of another elderly woman, Karen Courts, about a year earlier.

According to Ives, much like Ina’s case, there had been “quite a lot of violence” and the woman was stabbed to death. There were also no signs of forced entry at her home.

“I’m thinking this might be related,” he said. “It’s relatively rare to have elderly women being murdered in their own home, which started making me wonder is it possible the same perpetrator committed both crimes.”

But authorities hit another dead end after speaking to the detectives handling the Sarasota case. They learned that, although there were some slight similarities between the two cases, there were also some notable differences.

In Court’s case, there had been items stolen from the house, including her car, and there had been something done to the body post-mortem that didn’t fit Ina’s death.

Ives concluded it was “not consistent” with Ina’s case and that there had likely been two separate killers.

Investigators consider unlikely suspect

There was one other person that had been on detective’s radar from the very beginning — Ina’s son Tom.

According to Ives, Tom’s demeanor had been “a little different” from what you’d expect from a grieving son during his interview with investigators.

A neighbor also reported seeing Tom in the garage with the car running after 11 p.m. that night while out walking her dog, calling into question his version of events that night.

While investigators may have been suspicious, Gerth was convinced her brother had nothing to do with the crime and said Tom and Ina had a “very close relationship.” He even once saved her life on a family skiing trip after she got hit in the head with a T-bar on the slope, packing the wound with snow and ice until help could arrive.

“My brother is scared at this point that they believe it’s him. He said, ‘They think I did this’ and I am thinking that’s impossible,” she told the show. “My brother was stuck in a bad situation. He was just at the wrong place at the wrong time. My brother would never kill my mother.”

With no definitive proof he was involved, Tom returned to Israel just one day after the memorial service.

Their prime suspect may have been no longer been in the country, but that didn’t stop investigators from diving deeper into the mysterious case. They learned the vomit had been from Ina herself and in March, two months after her death, the medical examiner determined that there was Ambien and Benadryl in her system.

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"The amount of Ambien identified from the vomit is 5 to 10 times the amount that would normally apply in a normal therapeutic dose and could cause drowsiness and nausea,” Arthur Brown, the assistant state attorney for Manatee County told Killer Relationship with Faith Jenkins.

Strangely, however, Ina didn’t have a prescription for Ambien and wasn’t known to ever take it.

With the information in hand, detectives began to believe that Tom had drugged his mother, then placed her into the car and turned on the engine, hoping the carbon monoxide would finish the job. But, at some point, Ina must have regained her senses, vomited in the vehicle, got out of the car and tried to get back in the house.

“So, then he panics, just grabs a knife off the knife block. He goes into the garage and she’s standing there and he sets on her from behind and cuts her throat,” Ives said.

The toxicology results were also enough to have Gerth rethinking her brother’s innocence.

“When this information was revealed to me, I had this moment where I learned that my mother had been drugged. I realized that my brother had murdered my mother, but my heart did not want me to believe this,” Gerth said.

Tom Gross' motive is revealed

She eventually worked with detectives to bring her brother down by supplying the likely motive in the case. Detectives learned from Gerth that Tom had borrowed a staggering $668,000 from his parents before Ina’s death and did not have the financial capability to pay it back.

Ina’s friends also told authorities that Ina had planned to cut her son off financially and wasn’t planning to loan him any more money.

“Tom wanted that money and he probably needed that money to get him out of some new debt,” neighbor Marsha Tenret said.

Detectives finally had what they needed to make their case, but it would take seven long years to extradite Tom back to the United States.

He finally went on trial in May of 2022 and was convicted of first-degree premeditated murder and sentenced to life without parole.

“Thomas Gross is a cold-blooded killer,” Kenney said. “Who kills their mother? I mean it’s just beyond belief to me.”

While the loss is still agonizing for Gerth, she takes comfort in knowing her mother and father have been reunited in death.