He may have died facing his two greatest fears — dogs and water.

Missing autistic teen Avonte Oquendo was seen running from a dog at a nearby park right after he slipped out of his Queens school, and he likely fell into the East River in his panic, law-enforcement sources told The Post Friday.

The drowning scenario is the top theory for Avonte’s disappearance and was further substantiated when body parts and clothing believed to be Avonte’s were found 11 miles up-river from the park, on a beach in northern Queens.

“He had a huge fear of dogs and was seen running from one” in Hunter’s Point South Park, a short walk from his school, the source told The Post of the mute, timid 14-year-old.

“He may have run in a panic and fallen into the water,” of which he was also terrified, the source said.

The final surveillance video of Avonte shows him leaving his school in Long IslandCity and walking ­toward the riverfront park.

On Thursday night, a left arm and two legs — still inside their jeans and sneakers — along with pieces of a torso were discovered washed up off of College Point by a 19-year-old ­photography student.

The waterlogged size-5¹/₂ Nike Air Jordan sneakers and size-16 black jeans and striped shirt, both from Old Navy, all recovered from the remains site, match what Avonte was wearing when he went missing on Oct. 4, law-enforcement sources and the Oquendo family lawyer say.

The grisly evidence has been sent to the medical examiner, and DNA results will be complete by Wednesday, the family lawyer, David Perecman, said Saturday morning.

“It’s not looking great, Perecman conceded, updating reporters at the Rev. Al Sharpton’s National Action Network. Maybe it’s possible that it will be some sort of closure.

“The ‎police department assures me that by Wednesday the DNA will have been evaluated and we will know.”

The boy’s family members are still holding out hope that Avonte is still alive, the lawyer added.

“I have to say it for Vanessa (Fontaine, the mother) and Danny (the father) and the brothers. It’s not Avonte until the DNA evidence comes in and says it is,” the lawyer added.

Still, even Perecman slipped into past tense in referring to the boy Saturday, in a reference to how Avonte “was” autistic.

The family is continuing to pursue a civil claim against the Avonte’s school, the RiverviewSchool in Long IslandCity, and the city, he said, repeating several apparent oversights on the part of staff that could have kept the boy from disappearing.

“I’ve also received some information, finally, from the Department of Education,” he told reporters. “I’ve watched some of the video tapes they’ve provided us with. It just becomes more and more distressing when you see what happened. It appears that people involved were not being forthright about what they knew about Avonte missing, and it may have affected the ability of the school to find him. And if he did go in the water near the school, that time was precious,” he said.

“Until I look at these tapes again, I can’t say it for 1000% sure, but I have looked at them and I was talking to someone who’s very knowledgeable about what they saw in the tapes, and it appears that the tapes that I was given are not complete,” Perecman said.

“And that the thing that may be missing is what Commissioner Kelly spoke about, the confrontation, or the conversation, the brief one, between Avonte and the school safety agent where she saw him leaving the building,” he said.

“You can’t see in the tape that she says ‘Hello’ to him, she says ‘Where are you going?.’ She apparently says, ‘Go back to class.’ But she claimed to have seen him go up the stairs and stay in the school. That’s why the school was looking for him in the school. The problem is, the video tape shows he went out of the school. So she couldn’t have seen him go up the stairs. She could’ve said, ‘I think he went up the stairs. He went in the direction of the stairs.’ But she certainly didn’t see him go up the stairs,” he said.

“It does appear that she was seated at the table and the screen was in front of her, and she would’ve been able to see him walk out of the school. And in the video tape, she does go over to the door that he walked out of, two to three minutes after he walked out of it, and closes it. Very distressing information.”

Avonte walked out of his school undetected, through a side door, and was last seen on video heading toward the park.

The school safety officer is not suspected of misconduct, police have said.

The body parts were first spotted by Natasha Shapiro, the photography student, who lives nearby.

Shapiro, who takes classes at the Fashion Institute of Technology, had been snapping pictures of the beach at around 7:30 p.m.

“How do I get myself involved in these things?” she posted on her Facebook page Friday after being repeatedly grilled by cops.

“I just want to be left alone,” the rattled young woman told reporters outside her home later Friday. “I called police. That’s it. I want nothing else to do with any of it.”

Additional reporting by Erin Calabrese, Laura Italiano, Aaron Feis and Dana Sauchelli