The Atlanta Falcons explained on Sunday that the son of defensive coordinator Jeff Ulbrich was responsible for the prank call made to NFL draft pick Shedeur Sanders.

The Falcons released a statement saying 21-year-old Jax Ulbrich “unintentionally came across the draft contact phone number for Shedeur Sanders off an open iPad while visiting his parents’ home and wrote the number down to later conduct a prank call”.

Though Jax Ulbrich provided the number, he was sitting beside an unidentified friend who actually made the call to Sanders.

The Falcons said Jeff Ulbrich was unaware of the data exposure or the prank until after the fact. They offered “sincere apologies to Shedeur Sanders and his family” in their statement, and Jax Ulbrich also posted a public apology on social media.

Sanders, a standout quarterback from Colorado, is the son of Buffaloes coach and Pro Football Hall of Famer Deion Sanders, who began his NFL career with the Falcons.

Shedeur Sanders was perhaps the draft’s biggest story as he had to wait until the fifth round on Saturday before being drafted by the Cleveland Browns.

He received a prank call on Friday night, the second day of the draft, while waiting.

In the call, Jax Ulbrich’s friend identified himself as New Orleans Saints general manager Mickey Loomis and told Sanders he had been drafted by the Saints before ending the call.

“It didn’t really have no impact on me because it was just like, OK. I don’t feed into negativity or I don’t feed into that stuff,” Sanders said Saturday after being drafted.

“This is what it is. I think, of course, it’s childish, of course I feel like it was a childish act, but everybody does childish things here and there.”

Jax Ulbrich apologised to Sanders on Sunday for what he called “a tremendous mistake”.

“Shedeur, what I did was completely inexcusable, embarrassing and shameful,” he wrote on social media.

“I’m so sorry I took away from your moment, it was selfish and childish. I could never imagine getting ready to celebrate one of the greatest moments of your life and I made a terrible mistake and messed with that moment. Thank you for accepting my call earlier today, I hope you can find it in your heart to forgive me.”

The Falcons also apologised to Sanders and his family, saying they “do not condone this behaviour”.

“We are thoroughly reviewing all protocols, and updating if necessary, to help prevent an incident like this from happening again,” the Falcons said.

The Falcons said they have been in contact with the NFL “and will continue to cooperate fully with any inquiries we may receive from the NFL league office”.

Jeff Ulbrich celebrated the Falcons’ emphasis on defense in the NFL draft. The Falcons selected two edge rushers, Georgia’s Jalon Walker and Tennessee’s James Pearce Jr, in the first round. Their first four draft picks were defensive players.

Ulbrich was 3-9 as interim coach of the New York Jets last season before being hired to return to Atlanta, where he previously worked as an assistant.