LANSING, Mich (WLMI) Three teens are in custody after Lansing police say they robbed a woman of her purse at gunpoint.  The woman was walking along East Kalamazoo early yesterday morning when the suspects pulled up in a car, pulled a gun and demanded her purse.  After she refused to give up the purse—the teens got out and beat her up.  They were arrested a short time later.