Ask a Psychiatrist and Get Answers to Mental Health Questions ASAP
One of the hallmarks of BPD are continued threats or attempts of suicide when depression hits. It can be very scary.
That said, every threat must and should be taken seriously. Many people with BPD successfully commit suicide every year. My recommendation is to take him in to the Emergency Room or to an on-call therapist as soon as possible.
Best of luck to you and your family,