El Paso and Dayton Mass Shootings: Live Updates

For more than a few, and for women in particular, these signs were not hard to find.

“I don’t want to say I saw it coming,” said Mika Carpenter, 24, who met the gunman, Connor Betts, 24, at a summer camp when they were both 13. “But if it was going to be anybody it was going to be him.”

Like others who knew Mr. Betts as a teenager, Ms. Carpenter recalled his dark and often violent jokes, including riffs about “bodily harm” that led many to keep their distance.

“He was kind of hateful to women because they didn’t want to date him,” she said. Still, she became friends with him because, she said, she saw that he had a good side.

Mr. Betts often expressed concerns to her about having dark thoughts, she said.

“I remember specifically him talking about being scared of the thoughts that he had, being scared that he had violent thoughts,” said Ms. Carpenter, who cut off contact with him in 2013 after he lashed out at her during an online chat. “He knew it wasn’t normal.”

The police in Dayton were quick to caution on Monday that much about the shooting early Sunday morning was still unknown. There was still no clear motive, nor an understanding of how three people — Mr. Betts, his sister and a mutual friend — all went out together and one ended up shooting the other two. The friend, who has not been named by the police, was shot in his lower torso but survived; the sister, Megan Betts, 22, was killed.

[“It seems to just defy believability that he would shoot his own sister,” Dayton’s police chief said of the gunman.]