Stephen's death in Acts is a violent and sudden one, the kind of death which would leave you reeling and shocked if it were put on film. Some people confront him suddenly, while he may have been doing some good work or whatever, and drag him before a council against his will (6.12). He's forced to testify regarding some accusations unfairly made against him (vv. 13-14). His long speech ends in polemics, and he only makes his accusers angrier and more violent (7.54). They rush towards him, drag him out of the city and stone him to death (v. 58).
His death is sudden, unexpected, shocking, and violent; it's the kind of death you don't want to die. More than that, his death was just the beginning of a more widespread persecution of the disciples of Christ (8.1). The persecution was so great that, apart from the apostles, the disciples were scattered into the surrounding countryside to find refuge (v. 1).
But here's the interesting thing: those who were scattered went from place to place, proclaiming the word (v. 4). Stephen was just killed in cold blood outside the city gates for this word, they are dispersed and separated from one another, and this motivates them to go on preaching!
Here we have a fine example of the motivational power of martyrdom: when one of ours is willing to die for the cause, this moves us faithful few to pick up the torch where he left off, to keep on preaching even when the going gets tough. This also speaks to the reality of the earliest disciples' experience of Christ and the Holy Spirit: threats of violence and persecution, even the murder of one of their shining stars -- all these are not enough to stifle the fire burning with them, that people know the good news of Jesus Christ's resurrection.