VANCOUVER, Wash. (KOIN) — A 16-year-old charged with murder in connection with a deadly Vancouver robbery showed signs he was capable of extreme violence years ago, a local woman told KOIN 6 News.

Jaycob Trotter and another teen reportedly arranged to sell marijuana to 16-year-old Cesar Ortiz-Velasco in a parking lot on Friday, but they robbed him instead.

After grabbing his money, Trotter and the other teen drove off, running over Ortiz-Velasco. The 16-year-old later died at the hospital, prosecutors said.

Days after the deadly robbery, Amy Gardner said she wasn’t surprised Trotter was facing murder charges. She said she felt angry and frustrated after hearing about the killing, because she warned people for years that it might happen.

“This kid displayed every bit of violence you can imagine,” Gardner said.

The Vancouver mom said Trotter violently attacked her son 3 years ago, leaving him with a broken arm. She said his friend had even recorded the assault.

Trotter was 13 at the time, and charged with felony assault. He ended up serving 15 days in a juvenile detention center and 36 hours of community service.

But Gardner said she knew the incident was only the beginning. She showed KOIN 6 News letters she sent to prosecutors, pleading with them to do more. If Trotter and his family weren’t held responsible, she warned, “I assure you’ll continue to see him over and over. Hopefully for Jaycob’s next victim’s sake, he doesn’t kill them.”

In the wake of Ortiz-Velasco’s death, Gardner said, “the system failed everybody.”

“They failed, they dropped the ball. I told them this kid was incredibly violent,” she said. “They had a chance to correct the situation and they didn’t.”

Clark County Deputy Prosecuting Attorney Abigail Bartlett said the plea deal Trotter was given 3 years ago actually got prosecutors what they wanted: 12 months probationary supervision, rather than a short stint in juvenile prison.

“We did listen to Ms. Gardner… His sentencing range would have been 15-36 weeks, so about 3-6 months… and then he’s released,” Bartlett said. “There’s nobody keeping an eye on him after he gets out. And that’s by our state law.”

But Gardner said she wants her story to serve notice that someone else’s son is dead, and the teen who terrorized her boy is being charged with the crime.

“They had the video,” she said. “I talked to them so often.”

Trotter is being held on $500,000 bail and is being tried as an adult. The other teen involved in the incident was arraigned Thursday in juvenile court.