>> no nation can allow its borders to be overrun. and that's an invasion. >> reporter: the situation slowly simmering for weeks as the caravan drew closer, finally reaching a boiling point at the border. >> happening now breaking news. border escalation. president trump is defending the use of tear gas against migrants who rushed toward the u.s. bord border. >> reporter: thousands of asylum seekers are still there, waiting and hoping in makeshift camps and shelters. >> he says if he goes back to honduras they'll kill him. >> reporter: number 6, in march a former russian spy and his daughter were found on a park bench in salisbury, england, poisoned with the toxic nerve agent novichok. >> a former double agent sergei skripal and his daughter are in critical condition. they were found slumped over on a park bench. >> reporter: after investigating britain said the russian government was behind the attack. >> the two individuals named by the police and cps are officers