Three juveniles and a 19-year-old man planned for days before taking two guns from one of their homes earlier this month and forcing their way into the Groton home of two men they believed to be marijuana dealers, according to town police. 

Details of the March 6 home invasion/robbery at 139-8 Crystal Lake Road are contained in a probable cause report in the court file of Owen DeCosta, 17, of 405 Mohegan Ave., New London, who is accused of conspiring with Christian Cruz, 19, Samson Normandin, 17, and David Preston, 16, all of 22 Miner Lane, Waterford, to rob the Groton home of Zachary and Timothy Crawford. 

Due to the seriousness of the charges, DeCosta, Normandin and Preston will be tried as adults. 

DeCosta, who is being held in lieu of $200,000 at the Manson Youth Institution, appeared Tuesday in the New London court where major crimes are heard. Cruz, Normandin and Preston also are being held at the Manson Youth Institution and have upcoming court dates. 

During his brief court appearance, DeCosta stood with his mother, who was appointed as his guardian due to his age, and his appointed attorney, Matthew G. Berger. He previously had pleaded not guilty to home invasion, conspiracy to commit home invasion, first-degree burglary, conspiracy to commit first-degree burglary, conspiracy to commit first-degree robbery, criminal use of a firearm and second-degree assault. His next court date is April 9. 

According to the police report, Anthony J. McLaughlin-Lawrence, Samuel Tucker and Timothy Crawford were holding down DeCosta when town police went to 139-8 Crystal Road in Groton for a report of an armed robbery about 9 p.m. March 6. 

The alleged victims yelled that DeCosta and others had attempted to rob them and pointed to a Beretta 9 mm handgun they said DeCosta was carrying and a black ski mask that they said he was wearing. 

A fourth male, identified as Zachary Crawford, was bleeding from lacerations to his forehead. DeCosta also was bleeding and was taken to Lawrence + Memorial Hospital. 

The alleged victims said DeCosta entered through the front door, pointed the pistol at Zachary Crawford and announced it was a robbery. DeCosta struck Crawford in the head and the three other occupants of the home jumped DeCosta, fearing they were going to be shot. The victims said two other men who had entered with DeCosta, one of them carrying a gun, fled. 

Approached by police, DeCosta’s mother, Angela Dorsey, said she feared her son had stolen the recovered 9 mm pistol and a shotgun from their residence and used the weapons to commit the robbery. Police found the shotgun in a dumpster around the corner from the robbery scene after Normandin admitted they had thrown it there, according to the report. Normandin said Preston had been carrying the shotgun during the robbery. The police also found a duffel bag belonging to Preston in a nearby parking lot, according to the report. 

DeCosta admitted to discussing the robbery plans for “numerous days,” according to the report, and to striking Zachary Crawford with the pistol.