MAYWOOD, Ill. (WGN) — The search continues for a missing former NFL player whose mother was found dead in a creek in Chicago’s western suburbs over the weekend.

Authorities say they are searching for 35-year-old Sergio Brown, a Proviso East graduate who played in the NFL from 2010 to 2016 with the New England Patriots and Indianapolis Colts.

He was reported missing alongside his mother, Myrtle Brown, hours before she was found dead.

A new post appeared Monday on an Instagram account that is believed to be run by Sergio Brown. In the post, which was shared as a story, Sergio Brown apparently makes vague statements regarding the FBI and Maywood police and claims that he thought his mother was on vacation.

The Cook County Medical Examiner’s Office reported that Myrtle Brown died in an assault and that a homicide investigation into her death is underway.

“You just feel for the family, what they’re going through,” said Angel Rivera, a neighbor who lives across the street from the Brown family.

Rivera said he was shocked to find out about Myrtle Brown’s death.

“Saturday morning, when my wife told me Myrtle was missing, I was floored,” Rivera said. “We saw the commotion and realized that they had found the body and there were police everywhere.”

Myrtle Brown’s sister, Sheila Simmons, spoke with Nexstar’s WGN on Saturday hours after she got a call that both Myrtle and Sergio Brown were missing.

“It’s devastating,” Simmons said. “I walked around the house and I saw things that looked out of the ordinary.”

Simmons said she didn’t find anything after searching the creek behind Myrtle Brown’s house, but later in the day, she and other family members went back to search and discovered Myrtle Brown’s body.

“Later on, we got a group together and that’s when we found my sister in the creek dead,” Simmons said.

The Brown family said police are reviewing video footage from around the house as part of their investigation.

“My sister is gone, that’s all I can say,” Simmons said. “I don’t know what happened.”

Police have not named Sergio Brown as a person of interest, but are asking anyone with information on his whereabouts to come forward.