Buffalo Bills defensive tackle Ed Oliver Jr. was arrested Saturday night for Driving While Intoxicated ... and to make things worse, cops say he was also illegally carrying a GUN in his truck.
22-year-old Oliver was stopped in Montgomery County, Texas at around 9 PM after someone called 911 and said the truck Oliver was driving was swerving dangerously close to a construction zone.
When Cops approached Oliver -- who was driving a Ford Super Duty pickup truck that was hauling a trailer with a dune buggy -- they say the NFL player had an open can of beer between his legs ... not a great start.
Then he allegedly bombed a field sobriety test -- which included standing on one foot.
During a subsequent search of Oliver's vehicle, cops say they found a pistol.
Oliver -- the 9th overall pick in the 2019 NFL Draft -- was arrested for DWI and unlawfully carrying a weapon.
Cops say he was taken to a local hospital for a blood draw to get his blood alcohol level before he was ultimately taken to jail.
We reached out to the NFL players rep for comment ... so far, no word back.
Oliver was a 3-time 1st team All American in college during his days at the University of Houston.
He put together a pretty solid rookie campaign with 5 sacks and 43 tackles.