Oct. 18 (Bloomberg) -- Police in Marshfield, Massachusetts, arrested the 18-year-old son of the head of Boston's largest police union in connection with a suspected Columbine-style plot to attack a local high school.

Joseph T. Nee pleaded innocent to charges of conspiracy to commit mass murder and promotion of anarchy at his arraignment today in district court, Plymouth County District Attorney Timothy J. Cruz said in a telephone interview. Nee is being held without bail in the county house of correction until a hearing later this week on whether he is a danger to the public and should remain jailed, Cruz said.

Nee's father, Thomas J. Nee, president of the Boston Police Patrolmen's Association, is bearing up under the strain of his son's arrest, an attorney for the suspect said.

``He's doing as well as any father would be doing under similar circumstances,'' said Eric Goldman, an attorney with the Boston law firm Finneran, Byne & Drechsler LLP. Goldman said he didn't want to comment on details of the case.

Second Suspect

Nee is the second person held in the school plot that police in the Boston suburb described to reporters on Oct. 6. A 16-year- old juvenile was arrested in September and charged with planning an attack to take place on the anniversary of the April 20, 1999, massacre at Columbine High School in Littleton, Colorado, the worst school shooting in U.S. history.

In that incident, students Eric Harris, 18, and Dylan Klebold, 17, used an assault rifle and sawed-off shotguns to kill 12 students and a teacher before committing suicide.

Marshfield is located about 30 miles south of Boston on the Atlantic coast and has five elementary schools, one middle school and the high school.

Cruz said Nee was one of the students who originally went to police in September warning of an attack.

That tip led to the arrest of the 16-year-old student at the high school, police said.

The police statement said Nee and the juvenile are the two primary members of the plot to attack the school. Police said they consider Nee as dangerous as the juvenile.

``The Marshfield Police believes we now have the two principals,'' the statement said. ``The Marshfield schools continue to be safe,''

Investigators are still looking into the suspected plot and may file additional charges against Nee and the teen, the statement said.

Thomas Nee said outside the court today that he would support his son. ``I don't care what kids talk about, as long as they don't act it out,'' he said, according to the Associated Press. ``I'm just thankful for one thing, that there's been no tragedy, there's been nobody hurt.''

Hit List

According to information taken from the juvenile's computer, the plans included a hit list of students and teachers, a map showing which doors would be padlocked and information on how to build bombs and buy guns, police Lieutenant Phillip Tavares said at a press conference announcing the initial arrest.

Evidence was also discovered that the juvenile had tested a homemade bomb in preparation for the attack, Tavares said.

Police officials said they asked the court for a warrant to arrest Nee based on their investigation of material seized from the juvenile's home and his computer. Both teens were members of a group called ``Natural Born Killers,'' unidentified officials told WCVB, a Boston television station.

Boston Police Patrolmen's Association officials declined to comment on the case and said Nee wasn't available to take calls. Messages left at his home and cell phone weren't immediately returned.

The Boston Police Patrolmen's Association represents 1,428 police officers. Nee and the union gained national attention in July when they threatened to disrupt the Democratic National Convention in Boston because of a contract dispute.

To contact the reporter on this story: Brian K. Sullivan in Boston at bsullivan10@bloomberg.net

Last Updated: October 18, 2004 18:11 EDT