Calcutta, Nov. 6: Police struggled to put a face to the masked stalker who attacked engineering student Garima Singh at Jadavpur University on Wednesday even as psychiatrists painted the portrait of a young man suffering from borderline personality disorder.

“This seems to be a case of borderline personality disorder or BPD, which is more common than you think. We come across two or three persons suffering from mild to moderate BPD every day,” said city-based psychiatrist Ranadip Ghosh Roy.

According to doctors, Garima’s assailant was probably prone to “instability” in mood, interpersonal relationships and general behaviour.

“In most cases, behaviour changes abruptly if such people don’t get something they desire,” explained Ghosh Roy.

Investigators haven’t yet spoken to Garima about the possibility of her having met the stalker before but psychologists said the assailant was most probably someone whom she had “rejected”.

“Stalkers are usually unable to control their impulse and aggression after being rejected, and tend to exhibit extremely hostile behaviour. In most cases, they don’t have anyone to share their frustration with, which is the root cause of such behaviour,” said psychologist Tapashi Mitra.

Garima, who suffered a cut on her chest when the stalker tried to slash her with a blade in the second-floor corridor of the electronics engineering department, had received love letters and calls from an unidentified admirer before the attack.

The letters have been handed over to the police but investigators are waiting for the Shillong girl to “get back to normal” before interrogating her. “We have not been able to speak to her because she is still in shock,” said S.K. Chaudhury, the additional superintendent of police of South 24-Parganas.