Former NFL player Sergio Brown, who has been missing since his mother was found dead last month, has been arrested and is expected to face a first-degree murder charge in the killing once he is extradited from California to Illinois, police say.

Police in the Chicago suburb of Maywood, Illinois, issued an arrest warrant for Sergio Brown in connection with the killing of his 73-year-old mother, Myrtle Brown. The mother's body was discovered in a creek on September 16, police said.

Brown, who had traveled to Mexico, was taken into custody by Mexican authorities and deported to San Diego, California, where he was arrested on Tuesday, a law enforcement source familiar with the investigation told CNN.

The retired athlete is now awaiting extradition from San Diego to Maywood, where he will face the murder charge, police say.

CNN has been unable to determine if Sergio Brown has legal representation.

Here's what we know.

Brown's mother was found dead near their shared home

Both Sergio and Myrtle Brown were reported missing on September 16 by relatives who became concerned after they had not been able to find or contact the pair, police said.

That day, police went to search the home Sergio and Myrtle shared and found the mother's body's near a creek not far from the residence, authorities said.

Myrtle Brown had died from injuries sustained during an assault and her death was ruled a homicide, according to the Cook County Medical Examiner's Office.

Three days after Myrtle Brown's body was found, police told CNN they were aware of at least one video circulating on social media that appears to show Sergio Brown in a tropical location rambling about "fake news" and claiming he thought his mother was on vacation. It is not clear where or when the video was taken. Police did not confirm to CNN the person in the video is Sergio Brown and said they were investigating the video's authenticity.

Last week, Myrtle Brown's family released a statement urging officials to advance the case and saying police had sufficient evidence to make an arrest in the case.

"No family should bear the weight of uncertainty regarding the circumstances of their loved one's passing," the family statement said.

The family said they have not been in contact with Sergio Brown since his disappearance.

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

Brown caused a disturbance on his deportation flight, source says

Mexican law enforcement officers have known Brown's whereabouts since at least September 19 but were not able to deport him until Illinois authorities obtained a warrant for his arrest, the law enforcement source told CNN.

But Brown's transfer to the US did not go off without a hitch.

The former pro footballer created a disturbance on an extradition flight transporting him from Mexico City to Tijuana which prompted the pilot to threaten to remove him from the plane, the source said.

Once across the border in San Diego, Brown was taken into custody with the assistance of local and federal law enforcement, Maywood police said.

San Diego Sheriff's Department inmate records indicate Brown is being held by the agency on a felony fugitive arrest warrant and is scheduled to appear in court on November 13.

US interstate extradition laws require a hearing to be held if a defendant does not waive extradition, meaning a court may need to sign off on Brown's removal from California to Illinois.

Myrtle Brown remembered as caring, outgoing

Myrtle Brown's family said the killing of their beloved matriarch has "forever altered the course of our lives."

"Myrtle was a beautiful, loving, and inspirational soul that made everyone around her feel like they mattered. With her contagious smile and personality, our loss of Myrtle has left an indescribable void not only in our lives, but in our communities," the family said in its statement.

Her other son, Nick Brown, told CNN last month that his mother left him with a piece of wisdom that has become invaluable after her death.

"Mom always told me, 'tough times don't last' and our last conversation about tough times being temporary is my beacon of hope," Nick Brown said.

"Mom, thank you for being strong, caring, diligent, fancy, funny, and for saving my art. I won't let you down," he added.

The family said it is grateful for the outpouring of support as they seek justice for Myrtle Brown.

"Let us work together to turn this tragic loss into a force for positive change and justice," the family said.