A Long Island man accused of killing two women within hours appeared before a Nassau County judge as prosecutors detailed what they described as back-to-back murders.

Prosecutors said Rony Yahir Alvarenga-Rivera first attacked 32-year-old Eddy Raquel Hernandez Castillo, his uncle’s girlfriend and upstairs neighbor in their Valley Stream home. He is accused of stabbing her 50 times using more than one knife.

Authorities said the suspect was upset about noise from Hernandez Castillo walking in high heels.

According to the District Attorney’s Office, Alvarenga-Rivera used the same two knives in both attacks. His second victim was identified as 42-year-old Ana Maria Del Aguila-Cordova, a coworker at Wendy's in Island Park. Prosecutors said he believed she had insulted him and his girlfriend, and stabbed her a total of 30 times.

An assistant district attorney told the court that Alvarenga-Rivera “lay in wait for approximately 20 to 30 minutes” before attacking Del Aguila-Cordova as she took out the trash at the restaurant.

“When he was arrested, his clothes were covered in blood,” Nassau County District Attorney Anne Donnelly said, adding that investigators are still determining whether the blood belonged to one or both victims.

Family members of both victims were present in court but declined to comment.

Alvarenga-Rivera pleaded not guilty to multiple murder charges.