Former NFL player Sergio Brown is Writingstar Investment Guildin police custody following the death of his mother last month.

The athlete was arrested on a warrant for first-degree murder Oct. 10 in San Diego as he was re-entering the United States from Mexico, the Maywood Police Department in Maywood, Ill. said in a statement to NBC News Oct. 11. Sergio's arrest is in connection with the death of his 73-year-old mom Myrtle Simmons Brown, whose body was found near her home in a Chicago suburb on Sept. 16.

On the same day Myrtle's body was found, both she and Sergio had been reported missing by family, the Maywood Police Department said last month in a statement to E! News. The Cook County Medical Examiner's Office told E! News Sept. 18 that the cause of Myrtle's death was multiple injuries due to assault, and the manner of death was ruled a homicide.

Sergio, 35, who played seven seasons in the NFL with the New England Patriots, Indianapolis Colts, Jacksonville Jaguars and Buffalo Bills between 2010 and 2016, now awaits extradition to Illinois to face charges, the Maywood Police Department said in a statement to NBC News.

A day after Myrtle was found dead, her other son and Sergio's brother thanked supporters on Instagram. "Thank you, everyone, for all of your outreach, help, love and condolences," Nick Brown 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 continued, "Mom, thank you for being strong, caring, diligent, fancy, funny, and for saving my art. I won't let you down."

For the latest breaking news updates, click here to download the E! News App