They had a signing ceremony. There was a peace agreement. Peace in Burundi, however, is not at hand. On August 28 Nelson Mandela, the chief mediator in Burundi's peace process, managed to get a document signed in Arusha, Tanzania. Originally, the ceremony was supposed to end the state of civil and ethnic ware between Burundi's Tutsis and Hutus. US President Bill Clinton showed up for the photo op, then left.
At best Mandela's "Arusha agreement" is a very interim step in trying to solve very old and fierce troubles in central Africa. Mandela did succeed in getting a majority of Tutsi and Hutu parties to sign, but it is the "rejectionist" hard-core militants on either side that are prosecuting the war. Many active Hutu rebels demand what they call "direct negotiations" with the Tutsi controlled Burundi government. (These Hutus see Mandela as an unnecessary "third-party".) Tutsis reject what they call "Hutu guerrilla" participation in the Burundian Army. The Arusha agreement called for creating a Burundian army that is half Tutsi and half Hutu. For the record, the key Hutu guerrilla group, the FDD, did not sign the peace agreement though the FDD has told Mandela it "supports" the agreement. The other main Hutu rebel group, the more extreme FNL (National Liberation Forces) did not participate in the signing or the negotiations. Four Tutsi parties (of the G10, Group of 10) signed the agreement. Two other Tutsi parties gave indications they would ultimately sign on. 
The agreement, however, lacks teeth. The agreement has no means for establishing or policing a ceasefire.