David Nicholson Jr. is still trying to figure out what happened Thursday night that left his joyful, smiling 6-year-old son dying at St. Mary Medical Center.

His son, Dayvon Taylor, had been taken to the hospital where he died of wounds from being beaten.

Police arrested 23-year-old Tyler Martin-Brand, an acquaintance of Dayvon’s mother, in Downey on suspicion of murder the same night.

Until now, Nicholson Jr. only knew Martin-Brand as “the coach” or “Coach Ty,” he said.

Dayvon’s mom and dad had worked out a co-parenting agreement outside of court, with his mother having full custody of him and his 4-year-old sister and their father seeing them regularly, Nicholson Jr. said. But around September, the visits stopped.

“It was always, ‘He’s with the coach, call back later,'” he said. At the time, he assumed his son was safe with the man.

He kept in contact with his kids on the phone and through Facetime and didn’t have any hint that his son might be the victim of any abuse, he said.

Dayvon’s grandmother, Gwendolyn Nicholson, said the last time she saw Dayvon was on Nov. 4 through Facetime. He was turning 6 that month.

“He was very playful, he liked to love and hug and play,” she said as Dayvon’s little sister clung to her side. “And he got along with all kids. He just wanted to love.”

She and her husband, David Sr., said they got a call Thursday night from the boy’s mother, who was too emotional to talk clearly. According to them, she ended up handing the phone to Martin-Brand, who told them that he was “chastising” Dayvon and “hit him a couple times in the chest.”

The grandparents rushed to the hospital from their home in South Los Angeles, but by the time they got there, Dayvon had died, Gwendolyn said. They didn’t know that Dayvon’s mother had recently moved with the kids from South L.A. to Long Beach.

Now the Nicholson family is urging parents to be careful about who they let take care of their kids.

“Watch your babies, watch your kids,” Nicholson Jr. said. “My baby didn’t have to go like this.”

Family members, neighbors and friends gathered Saturday night outside the Nicholson home to remember Dayvon with a candlelight vigil. Activist Najee Ali, who organized the event, urged women to not leave their children with men they were dating and to ask family to take them instead.

Nicholson Jr. said he has limited information from police so far, but he still needs to know what led to his son’s death.

“I’m still digging for answers,” he said.