PEMBROKE PINES, Fla. -- Doctors are trying to determine what kind of snake bit a man who was arrested on trespassing charges after acting erratically at a local elementary school.

Late Friday afternoon, Damian Hernandez Rubio was in extremely critical condition at Memorial Hospital West -- though he was showing some slight signs of improvement.

Around 1:30 p.m. Thursday, Pembroke Pines police were dispatched to Pines Lakes Elementary School, where Rubio, 31, was behaving strangely. As police were taking Rubio into custody, they noticed his breathing was interrupted and at one point stopped completely.

Rubio was rushed to the hospital, where doctors there determined he was suffering from snakebite. Although doctors were able to identify the problem, they could not determine what kind of snake bit him.

"In this case, he doesn't seem to be responding to the proper treatment of snakes native to the United States, so we're leaning to believe that it may be from another part (of the world)," said Miami-Dade fire-rescue Capt. Al Cruz with the anti-venom unit. "We carry 43 different anti-venoms that cover 98 percent of all the world's venomous snakes."

Cruz said that of the more than 400 snakebite victims the anti-venom unit has treated, Rubio's case is one of the top five worst. Rubio has been treated with more than 50 vials of anti-venom -- more than four times the average dose.

Police said Rubio would not be charged with trespassing, although he could die if doctors don't find out what kind of snake bit him.

School officials have checked the grounds but did not find any snakes. Cruz believes the snake might have been Rubio's pet.