Psychology of terror: Are terrorists born or made?

Britain has yet to recover from two horrific terrorist attacks by Islamic extremists – the explosion at Manchester Stadium, which killed 22 people and left hundreds others injured and the knifing two weeks ago, of weekend revellers by three attackers who first ran over pedestrians by driving their van over a sidewalk leaving in their wake eight people dead.

All these attacks - including those that Kenya has had to endure - leave us wondering if terrorists are normal human beings. What would make a person do irrational acts like blowing himself up in the name of passing a message to governments? What would make a person show no remorse for killing a fellow human being?