Authorities in Indiana have activated a Silver Alert for a missing 16-year-old boy who disappeared last week.

Robert “RJ” Williams Jr. was last spotted in Indianapolis on December 17, according to reports from WISH. On Monday, Indianapolis police shared that investigators found Williams’ gym bag and backpack on a dock by the White River one day after he went missing.

Williams, who has been diagnosed with autism and a mild intellectual disability, reportedly functions at the level of a 10- or 11-year-old, as detailed by the Indianapolis Star. He also has a history of psychosis and disruptive mood dysregulation disorder.

Concerns arose when Williams did not return home from Purdue Polytechnic High School. It is believed he visited a McDonald’s prior to his disappearance.

Described as 5 feet 9 inches tall and weighing 185 pounds, Williams has black hair and brown eyes. He was last seen wearing a gray coat, blue sweatpants, and black tennis shoes.

Anyone with details about Williams’ location is urged to contact the Indianapolis Metropolitan Police Department at 317-327-6541 or call 911.