Trinita Farmer spent part of Mother’s Day searching for the spot where her son died after being put in a chokehold by a Las Vegas police officer one year ago.

“Do you know where my son was killed at?” Farmer asked security guards at The Venetian, the Las Vegas Review-Journal reported. The grieving mom held a vigil for her son, Tashii Brown, outside of the luxury hotel on Sunday, marking the one-year anniversary of his death, which was ruled a homicide caused by asphyxiation.

Farmer now wants justice for Brown. On Sunday, she filed a federal lawsuit against the Las Vegas Metropolitan Police Department and officers Kenneth Lopera, Travis Crumrine, Michael Tran, and Michael Flores. According to the suit, Lopera put Brown in a chokehold for over a minute on May 14, 2017, while the other officers failed to intervene.

The father-of-two died later that night of asphyxia due to “police restraint procedures,” according to the Clark County Coroner’s Office. Brown’s mom alleges wrongful death in her lawsuit and is suing for emotional damages and attorney fees. Las Vegas Metropolitan Police Department declined to comment on the lawsuit, according to the Review-Journal.

Last May, Brown approached police officers near The Venetian, asking where he could find the nearest water fountain, the lawsuit states. When Lopera asked Brown why he was sweating, the 40-year-old man told the officer he thought people were following him.

Brown “displayed symptoms of mental confusion and appeared to be suffering from a mental disorder,” the lawsuit states. He ran away from Lopera, who chased him through The Venetian parking lot, according to the suit.

Lopera later claimed that Brown tried to steal a car during the chase, but the owner of the vehicle told authorities that he didn’t believe Brown was trying to carjack him. At one point, Lopera cornered Brown, shocking him with a Taser seven times while telling him to get on his stomach, the lawsuit says.

“Officer Lopera told Tashii to get on his stomach several times but never gave Tashii a reasonable opportunity to comply with commands before cycling” the Taser again, according to the court papers. The officer also hit Brown in the face and head 12 times, the lawsuit states.

Lopera allegedly held Brown in a chokehold for over a minute, as other officers stood by without attempting to intervene. Officer Tran was the only cop who told his colleague to let Brown go, according to local reports.

“Is he out yet?” Lopera repeatedly asked as he strangled Brown, according to a report obtained by the Review-Journal. When Lopera let go, Brown was unconscious, the newspaper reported. He was pronounced dead at a local hospital later that night.

Since Brown’s death, police revealed that Lopera used a martial-arts-style chokehold that isn’t permitted by the department, The New York Times reported. Lopera, who retired from the department in October, was charged with multiple counts of involuntary manslaughter in July. Crumrine was demoted from sergeant to officer for his involvement, according to the Review-Journal.

Farmer is still grappling with her son’s death.

“[She] frequently must hurry and shut the television off when a story about Tashii is broadcast,” the lawsuit states. “Finally, every Mother's Day is and will be a reminder that her son was senselessly and illegally killed by Metro and its officers.”