"Steelers president Art Rooney II said it was difficult to "even comprehend" the controversial comments made by Rashard Mendenhall on Monday on Twitter, and a crisis communications expert said the running back would be "well-advised" to apologize.

Mendenhall ignited a firestorm when he questioned why people were celebrating the killing of 9/11 mastermind Osama bin Laden. Mendenhall, on the social media site, asked how people could "HATE" a man they had never heard speak and questioned whether the planes flown into the World Trade Center by terrorists could have brought down the Twin Towers.

Mendenhall's incendiary remarks drew a raft of criticism and compelled the Steelers to respond.

"I have not spoken with Rashard, so it is hard to explain or even comprehend what he means with his recent Twitter comments," Rooney said in a statement. "The entire Steelers' organization is very proud of the job our military personnel have done, and we can only hope this leads to our troops coming home soon."

Neither Rooney nor any of the Steelers' executives and coaches are allowed to contact Mendenhall during the NFL lockout. Mike McCartney, Mendenhall's agent, declined comment.

Gene Grabowski, a senior vice president at Levick Strategic Communications in Washington, said Mendenhall committed a common mistake among young celebrities that are on Twitter: He didn't think about the impact of his entries.

"I think Mr. Mendenhall would be well-advised to apologize as quickly as possible," said Grabowski, who's from Pittsburgh and graduated from Pitt. "The public expects and appreciates that athletes and celebrities will have opinions on issues, but where it becomes a problem is when an athlete or celebrity shares those opinions so freely without apparent regard for the sensitivities of people who have suffered loss or feel strongly about a subject."

The killing of bin Laden touched off mass celebrations across the country. Steelers chairman emeritus Dan Rooney, the U.S. Ambassador to Ireland, hailed the military operation that resulted in the demise of the world's most notorious terrorist."