carlos colina , 32 , pleaded not guilty to assault and improper disposal of a human body on monday after the remains were found near his building .
he was seen walking to his apartment in cambridge , massachusetts with the victim , jonathan camilien , hours before the remains were found .
colina also has an outstanding assault and battery case pending against him after he ` attacked a man at his gym and left him bloodied '
witnesses said colina had been intimidating other gym users for months .