Ms. Harper, who divorced her husband a decade ago, appears to have been by far the most significant figure in her son’s troubled life;
Unlike his father, who said on television that he had no idea Mr. Harper-Mercer cared so deeply about guns, his mother was well aware of his fascination.
In fact, she shared it: In a series of online postings over a decade, Ms. Harper, a nurse, said she kept numerous firearms in her home and expressed pride in her knowledge about them, as well as in her son’s expertise on the subject.
She also opened up about her difficulties raising a son who used to bang his head against the wall, and said that both she and her son struggled with Asperger’s syndrome, an autism spectrum disorder.
In an online forum, answering a question about state gun laws several years ago, Ms. Harper took a jab at “lame states” that impose limits on keeping loaded firearms in the home, and noted that she had AR-15 and AK-47 semiautomatic rifles, along with a Glock handgun. She also indicated that her son, who lived with her, was well versed in guns, citing him as her source of information on gun laws, saying he “has much knowledge in this field.”
Law enforcement officials have said they recovered 14 firearms and spare ammunition magazines that were purchased legally either by Mr. Harper-Mercer, 26, or an unnamed relative. Mr. Harper-Mercer had six guns with him when he entered a classroom building on Thursday and started firing on a writing class in which he was enrolled; the rest were found in the second-floor apartment he shared with his mother.
Neighbors in Southern California have said that Ms. Harper and her son would go to shooting ranges together
Ms. Harper said that her own son “was, among other things, a head-banger” when he was younger and was initially given a misdiagnosis of attention deficit disorder.
the gunman’s mother sometimes confided the difficulties she had in raising her son, including that she had placed Mr. Harper-Mercer in a psychiatric hospital when he did not take his medication.