Police released shocking video Saturday of a young robber viciously beating an elderly Bronx man, repeatedly pummeling him before snatching his jewelry and cash.The assailant grabbed 81-year-old Jose Rodriguez as he entered the lobby of his Parkchester building at around 4:00 p.m. Thursday and threw him to the ground."When I came in, he grabbed me by my throat with his left arm and he was hitting me with his right hand," Rodriquez told the Post. "I tried to defend myself, but he was behind me. I was taken by surprise."The thug repeatedly punched and kicked the elderly man in the head and struggled to pull cash from his pockets. He also snatched the victim's gold crucifix necklace as he made off with $30 in cash and Rodriguez's Medicare ID.Rodriguez was left with a blackened left eye and a swollen face, but a CAT scan showed he had no more serious injuries to his head."I couldn't talk or say anything, I was just trying to defend myself," said Rodriguez, a father-of-three and grandfather-of-two who is a retired boiler operator for the city.The robber escaped and was still at large Saturday. Police said he black, between 17 and 20 years old and was last seen wearing a dark blue T-shirt, blue jeans and black sneakers. He was wearing a black backpack during the attack.Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).The public can also submit their tips by logging onto Crime Stoppers website and at nypdcrimestoppers.com or by texting their tips to CRIMES (274637), then enter TIP577.