NEW : Possible Al-Shabaab Twitter account warns Nairobi the attack was only `` Act 1 '' Source : Investigators link a store rented in the past year to the attackers . CNN 's Michael Pearson reported and wrote from Atlanta ; Nima Elbagir reported from Nairobi ; CNN 's Neda Fashbaf also contributed to this report . Comment: At least 67 people are known dead ; as many as 61 remain unaccounted for .
NEW : Possible Al-Shabaab Twitter account warns Nairobi the attack was only `` Act 1 '' Source : Investigators link a store rented in the past year to the attackers . Comment: At least 67 people are known dead ; as many as 61 remain unaccounted for .