An accused heroin dealer sold an addict the drug, watched him die and then texted her mother to tell her, Portsmouth police said.Amanda Burgess, 25, sold Joseph Cahill, 27, a $40 bag of heroin, was with him when he injected the drug and then watched as he overdosed, according to a police affidavit cited by SeacoastOnline.com.Burgess, according to the affidavit, sold Cahill, a young father, heroin on June 14 and was with him the next morning when he injected the drug and quickly became unconscious."I just watch sum one die rite in front of me," the text from Burgess to her mother read, according the affidavit cited by SeacoastOnline. She then texted that she was going to "lay low" and catch a bus.Burgess' mother went to the Portsmouth police station later in the day and told investigators that her daughter "was with the boy when he died."Amanda Burgess, who was waiting outside the station, agreed to speak to police and was subsequently arrested on felony drug charges. She is being held on $100,000 bail.Cahill was the sixth person to die in Portsmouth of a suspected heroin overdose this year.