A 73-year-old Levittown woman was stabbed to death and her grandson was wounded in what's being described as a revenge plot over previous marijuana deals, authorities say. 

Benjamin Lopez, 23, of Levittown, and Deangelo Gill, 19, of Uniondale, each pleaded not guilty during their arraignment Thursday afternoon on second-degree murder charges. They are accused of fatally stabbing Lorraine Pizzichemi inside her North Newbridge Road home. 

According to authorities, this was a targeted event. Detective Lt. Stephen Fitzpatrick said Lopez felt like he was being ripped off in past marijuana deals. 

"Their intention was to rob the house of whatever marijuana and currency they had there, as well as to act out a revenge on the 24-year-old," says Fitzpatrick. 

Police say the two men viciously attacked the 73-year-old and then ransacked the home, looking for drugs and money. That's when they say the woman's 24-year-old grandson came home, and was beaten and slashed.

"They forced him to show them to a safe, where they obtained an unknown quantity of marijuana and currency," says Fitzpatrick. 

Police say the pair fled the house but were eventually arrested later at Lopez's home just around the corner.

Authorities say a 21-year-old woman was home at the time of the incident, but she was not harmed. The 24-year-old was transported to a hospital and is listed in serious condition.

Lopez's attorney says his client didn't do anything wrong and that the 24-year-old was the primary aggressor. 

Both men were held without bail and are due back in court on Sept. 18.