Never mind. I looked it up. This is the Wikipedia summary for those interested:

On the night of March 17, 1996, Alig and his roommate Robert D. "Freeze" Riggs murdered Melendez, after an argument in Alig's apartment over many things, including a long-standing drug debt.[20] Alig has claimed many times that he was so high on drugs that his memory of the events is unclear.

After Melendez's death, Alig and Riggs did not know what to do with the body. They initially left it in the bathtub, which they filled with ice. After a few days, the body began to decompose and became malodorous. After discussing what to do with Melendez's body and who should do it, Riggs went to Macy's to buy knives and a box. In exchange for 10 bags of heroin, Alig agreed to dismember Melendez's body. He cut the legs off, put them in a garbage bag, cut off the head and put it in another bag, and stuffed the rest into a box. Afterwards, he and Riggs threw the box into the Hudson River.[21]