WASHINGTON — Police are searching for a former NFL player after his mother was found dead at their home in a suburb of Chicago.

Investigators believe that Myrtle Brown, 73, was assaulted before she died. Her death has been ruled a homicide.

The whereabouts of her son Sergio Brown, 35, remain unknown. Police have not named him as a suspect.

Brown played for four professional teams during a six-year career in the NFL.

According to police in the town of Maywood — about 12 miles (19km) west of Chicago — officers investigating a missing persons report filed by family members discovered Ms Brown "unresponsive near a creek to the rear of her residence".

Her body was later transported to a medical examiner's office, where it was determined she had suffered from multiple assault injuries.

Mrs Brown's other son, Nick Brown, took to Instagram on Monday to plead for help as the search for his brother continues.

"If you have any information on Sergio's whereabouts please send them to the Maywood Police Department," he wrote.

"It's a sad but hopeful time, and we will all get through this together. Mom always told me, 'tough times don't last' and our last conversation about tough times being temporary is my beacon of hope."

He added that people should avoid the family's property in Maywood, which he said was still the scene of an ongoing investigation.

Police have not stated if Brown is a suspect or person of interest in the case.

In a bizarre turn of events first reported by a Chicago Fox affiliate, Sergio Brown has reportedly appeared on Instagram in a video from Mexico in which he calls reports of the murder "fake news".

In the rambling, sometimes incoherent video, Brown claims his mother was on vacation in Mexico at the time of the incident. He also accuses both the FBI and Maywood Police Department of involvement.

Hours later, Brown posted another video to Instagram that showed his location as Sydney, Australia.

The video — which appears on a separate account from his verified Instagram page — could not be independently verified by the BBC.

The BBC has reached out to the Maywood Police Department for comment.

Brown, a graduate of Notre Dame University, began his career with the New England Patriots in 2010. He went on to play for the Indianapolis Colts, Buffalo Bills and Jacksonville Jaguars before leaving the NFL in 2016.

Carlos Cortez, a local resident who last saw mother and son on Thursday, told CBS, the BBC's US partner, that the Brown family had told him that Brown "wasn't himself the last few months".

"He was out of his mind," Cortez said.

He added that footage from his doorbell camera was inspected by police and showed Brown "taking out the trash, and they see him have a bonfire, where he burnt all her clothes".

Police are now seeking the public's help to find Brown. — BBC