Carlos Cortez, a neighbor who said he last saw Sergio and Myrtle Brown in person on September 14, provided police with Ring doorbell footage, which reportedly shows Sergio Brown "taking out the trash" and having "a bonfire where he burned all her clothes."

"They said he wasn't himself the last few months. He was out of his mind," Cortez told CBS News.

Myrtle Brown was reported to be unresponsive near a creek behind her home on September 17 while authorities were searching for her and her son, police in Maywood, Illinois announced via NBC News. The elder Brown was reported to have been killed by "multiple injures due to assault" and her death was characterized as a homicide, the Cook County Medical Examiner's Office confirmed in an email on September 17.

Myrtle and Sergio Brown were both reported missing on September 16 after family members claimed they couldn't find or contact them, the Maywood Police Department said in a statement obtained by NBC Chicago. The elder Brown was located by authorities after the second round of a search launched to find the two individuals.

The police probe was characterized as a homicide investigation, however, the department's statement didn't categorize what led to that determination.

"Currently the Maywood Police Department is attempting to locate Mr. Sergio Brown," the department said.

Brown signed with the New England Patriots as an undrafted free agent in 2010 and spent his first two seasons with the franchise before signing with the Indianapolis Colts in 2012. The former Notre Dame standout spent three seasons with the Colts, as well as the 2015 season with the Jacksonville Jaguars and 2016 season with the Buffalo Bills.