(Credit: Dan Mullan/Getty Images/File)

(CNN) -- Former NFL player Sergio Brown is missing after his mother died of assault-related injuries and her body was found near a creek behind their home in suburban Chicago, according to police and records obtained by a CNN affiliate.

Authorities discovered the body of 73-year-old Myrtle Brown on Saturday after family members alerted police they had been unable to find her or contact her or her son, the Maywood Police Department said in a news release.

The Cook County Medical Examiner's Office determined Myrtle Brown died from injuries related to an assault, and the manner of death was ruled a homicide, records obtained by CNN affiliate WBBM show.

On Sunday, Sergio Brown's brother appealed for help on social media to find him.

"My brother Sergio is still missing," Nick Brown wrote on Instagram. "If anyone knows where he is, I want him to know that I love him and that I ask him to please come home."

As police responded, police tape blocked themselves on a residential street in Maywood, about 24 miles (1.15 kilometers) west of the Chicago Loop, a WBBM video shows.

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"Myrtle, she was an exceptional woman and I hope she's in the right place and with God," Carlos Cortez, Myrtle Brown's neighbor, told WBBM. "I would never have expected this in a million years."

Sergio Brown, 35, played for Notre Dame before signing with the New England Patriots as an undrafted free agent in 2010. He played seven seasons in the NFL as a member of the Patriots, Indianapolis Colts, Jacksonville Jaguars and Buffalo Bills.

Myrtle Brown (Nick Brown/Instagram)

"It's a sad but hopeful time, and all together we will get through this," Nick Brown wrote online. "Mom would always tell me, 'Hard times don't last,' and our last conversation about hard times being temporary is my ray of hope."

"Mom, thank you for being strong, loving, diligent, elegant, funny, and for saving my art. I won't let you down."

The investigation continues, according to Nick Brown, who asked people not to approach the family's property and to contact Maywood police with any information about his brother's whereabouts.

Anyone with information can contact an anonymous information line at 708-450-1787, police said. The lead investigator in the case, Dennis Diaz, did not respond to CNN's request for more information. CNN has reached out to members of the Brown family.

With information from Alisha Ebrahimji and Caroll Alvarado

American football