Police are searching for a suspect they think may have murdered a Queens teacher after they met online.

David Rangel, 53, was found choked to death and shoved under his couch in his Jackson Heights apartment Sunday, officials said.

A police spokesman said cops responded to a 911 call, after a friend checking on him found the door unlocked and ajar.

Police found Rangel with trauma to his head and blood on the floor and the walls.

Councilman Daniel Dromm asked the NYPD to investigate the murder as a hate crime.

“The horrific crime committed against David Rangel, an openly gay public school teacher who lived in one of the city’s most tolerant communities, is deeply distressing,” Dromm said.

Dromm spokesman Alex Florez said Rangel appears to have met someone online. The councilman’s concern is that someone may have targeted him because he is openly gay, and that this perhaps led into a potential bias-motivated murder.

“Something obviously went terribly wrong there,” Florez said.

Rangel taught seventh- and eighth-grade Spanish at P.S. 219.

“We are deeply saddened by the loss of a well-liked and respected teacher, David Rangel,” the school’s president, Fred Wright, wrote on Twitter yesterday.

Meanwhile, the family of a Staten Island woman, Sarai Sierra, is searching for her in Turkey, where she disappeared while traveling this month.

They, too, are concerned she may have met someone online. She had planned to meet with strangers she met through Instagram, according to the Daily News.

Online safety expert Hemu Nigam said that when people sit behind a computer screen, they may wrongly lower their guard.

“When you’re going online, it’s very much like you’re going down a New York alley,” he said. “You don’t know where you’re going, you don’t know what might pop up … yet when you’re on a computer, you do it without thinking twice.”

Use caution behind the computer screen

“If you’re connecting with somebody in the online world, unless you are seeing the whites of their eyes, they should be treated as a stranger to you,” Nigam said.

Instead, he said, when people talk online, they can feel very comfortable, because they are in the comfort of their own home. But people should have the opposite reaction. If something seems off, ask for clarification, he advised.

“I think your first best friend in all of this is Google,” he said. “You can see if the job they’re talking about actually exists. … if your instincts say there’s something wrong, you’ve got to go with it.”

He also suggests a face-to-face chat on the computer or phone. “If the person refuses because they’re giving you examples like, ‘My hair doesn’t look good today, I’m just not feeling well,’ your senses should go up,” he said.

If you do meet someone, perhaps through an online dating website, make sure it is in a public place, and consider having a friend show up two or three tables down or suggesting a group setting.

Danielle Tcholakian contributed reporting.