“At that moment,

The cock crowed.

Then Peter remembered

What Jesus had said.

‘Before the cock crows,

You will deny me

Three times.’

He went out.

He wept bitterly.”

καὶ εὐθὺς ἀλέκτωρ ἐφώνησεν.

καὶ ἐμνήσθη ὁ Πέτρος τοῦ ῥήματος Ἰησοῦ εἰρηκότος ὅτι Πρὶν ἀλέκτορα φωνῆσαι τρὶς ἀπαρνήσῃ με· καὶ ἐξελθὼν ἔξω ἔκλαυσεν πικρῶς

This is almost word for word in Mark, chapter 14:72, except that Mark has the cock crowing twice instead of once.  In Luke, chapter 22:60-62, not only does the cock crow, but Peter sees Jesus look at him to remind him of his failures.  John, chapter 18:27, has only the simple remark that the cock crowed when Peter denied Jesus the 3^rd time, without Peter weeping.  Matthew recounts that at that moment when the rooster cock crowed (καὶ εὐθὺς ἀλέκτωρ ἐφώνησεν), Peter remembered what Jesus had said (καὶ ἐμνήσθη ὁ Πέτρος τοῦ ῥήματος Ἰησοῦ εἰρηκότος).  Before the cock or the rooster crowed (ὅτι Πρὶν ἀλέκτορα φωνῆσαι), he would deny, disown, or repudiate Jesus 3 times (τρὶς ἀπαρνήσῃ με).  Thus, Peter went out and wept or lamented bitterly (καὶ ἐξελθὼν ἔξω ἔκλαυσεν πικρῶς).  The early followers of Jesus, the primitive Christian community, were in shambles.  Both Peter and Judas, two of the 12 leaders, had betrayed Jesus, while Jesus himself was about to be led off to death.