Murder Mystery - Mr. A and Mr. B

Mr. A and Mr. B are two friends walking on a deserted road at midnight.
They both argue about something and soon Mr. B kills Mr. A and rushes out of the place.
After sometime police and detective arrive at the spot.
The detective discovers Mr. A wallet and phones Mr. B after finding Mr. B's visiting card with his phone number in it.
He says "Sir, we have discovered a dead body here and we found ur visiting card in the dead person's wallet.
Please come here and identify the body".
After sometime Mr.B arrives there and the police arrest him.
How did they know he was the murderer???

Click here for Answer

They did not tell him where the murder took place but still he reached there.