ORLANDO, Fla. — It was a wrenching ritual that has become all too familiar for President Obama.

One by one on Thursday, inside an arena in downtown Orlando where friends and relatives of the victims of the nation’s deadliest mass shooting had congregated, Mr. Obama embraced mourners sick with loss. He told them that the nation stood with them and that his own heart was broken, offering words of comfort for a tragedy that he confessed he could not fathom.

“Their grief is beyond description,” Mr. Obama said after a two-hour meeting with the mourners. “Through their pain and through their tears, they told us about the joy that their loved ones had brought to their lives.”

Behind closed doors, Mr. Obama told the grieving that it was the 15th time during his seven-and-a-half-year tenure that he had had to offer these sorts of condolences after a shooting, according to those who attended.

“There were times when he choked up,” said Angelica Jones, a performer at the Pulse nightclub, where a gunman killed 49 people and wounded 53 on Sunday. “And it’s a hard thing to do when you’ve got mothers crying out. He was up to it.”