Why is life so unpredictable?

Life is so strange. The events happening in our lives are most unpredictable and we do not know what is going to happen the next moment. Everything is hidden from us.
News of terrible happenings reaches us from home and abroad jolting us deeply and question arises in our mind: why has this to happen?
On April 16, 2013 a terror attack was carried out on a sporting event in Boston, USA. Two bombs went off 13 seconds apart near the finishing line of Boston Marathon, killing three people and injuring 176 others, 17 of whom are in a critical condition.
They were enjoying the event, being unaware about the horror awaiting them.
We learned from The Daily Star that a man was killed and 10 others were injured as a container of Chittagong-bound freight train fell on a slum along the rail tracks in Dhaka's Banani area on April 18, 2013. The accident occurred at 12:30 pm when Majibur Rahman (35), a rickshaw puller, was sleeping with his son beside him. Majibur Rahman died instantly and his son is fighting for his life. How sad! When he went to sleep little did he know that he would not wake up again!
Death is inevitable, but we can not accept untimely and unnatural deaths. In fact, I wonder why we were created and why there is so much suffering--physical and mental. Almighty Creator is The Most Merciful and The Most Beneficial. But then why His creations have to go through pain and misery? I do not know if anyone has got the answer.